Heating and air conditioning systems are well known and developments to improve them are continually being sought. One type of such a system is a zoned heating and air conditioning system. In this type of system, the building structure receiving conditioned air is divided into a number of zones with each zone receiving conditioned air according to its needs.
For example, U.S. Pat. No. 5,181,653 to Foster et al discloses a residential heating and air conditioning control system for a multi-zone residence. The system includes a heating and cooling unit connected to a duct system which leads to registers in each zone of the residence. A master thermostat is provided at one location in the residence while slave thermostats are provided in each of the zones. Dampers are provided throughout the duct system to allow the flow of conditioned air into each of the individual zones to be controlled. The master thermostat is connected to each slave thermostat and receives signals from the slave thermostats in response to differences between the sensed temperatures in the zone and the set point programmed into the thermostat. Each thermostat includes a display for displaying the thermostat set point as well as the sensed temperature in the zone. The master thermostat has a switch to allow a display of the slave thermostat set points and the sensed temperatures in each of the zones. The master thermostat also allows the temperature set point in each zone to be preprogrammed for different times of the day. In operation, when a slave thermostat detects a difference between its set point temperature and the temperature within the zone, it provides a control signal to the master thermostat which in turn controls the heating or cooling unit and the damper associated with that zone to provide conditioned air.
U.S. Pat. No. 4,886,110 to Jackson discloses an HVAC zone control system which includes a number of heating units, a number of cooling units and a blower to force air through the units to distribution ducts. When it is desired to cool air expelled by the blower, only the cooling units are operated and when it is desired to heat air, only the heating units are operated. The distribution ducts feed the air to a number of separate zones. Each zone includes a damper which is either opened or closed. Within each zone is a thermostat which monitors the temperature in the zone and provides output signals to a microprocessor. The microprocessor examines the output of the thermostats to detect whether the zones require heating or cooling. When a number of zones exceeding a threshold number request heating, the dampers at the non-requesting zones are shut and the heating unit is energized. The number of heating stages in the heating unit that are energized depends on the number zones requesting heating. When the zones reach the desired temperature, the thermostats stop providing output signals to the microprocessor. The cooling operation works in a similar manner. In an automatic mode, the number of requesting zones for heating or cooling is determined by calculating the difference between the two. If the difference value exceeds the threshold then either heating or cooling is performed depending on whether more zones request heating or cooling.
U.S. Pat. No. 4,830,095 to Friend discloses a temperature control system for an air conditioning system. Thermostats are provided in each zone of the system along with associated dampers to control air flow into each of the zones. The thermostats provide control signals to a control unit when the temperature in the zone differs from the set point of the thermostats. In the specific embodiment disclosed in this patent, zone 1 and zone 2 are connected to a common circuit in the control unit such that when zone 1 needs conditioned air and zone 2 does not, the damper in zone 2 is closed while the damper is zone 1 is kept open and vice versa. If both zones require conditioned air, the dampers to both zones 1 and 2 are kept open. Priority can be appointed in the event that both zones request conditioned air so that the zone which has been given priority is the only zone which receives conditioned air even though both zones may be requesting conditioned air. The control unit also prevents situations arising where all dampers are closed with the fan and heating or cooling unit operating.
U.S. Pat. No. 4,673,029 to Beachboard discloses a zoned heating and air conditioning system having two zones and two thermostats. The system includes two basically isolated air conditioning units which supply conditioned air to their respective zone. In operation, when a thermostat in one zone detects that conditioned air is required, it provides signals to close the dampers in the other zone so that conditioned air is only received in the zone requesting conditioned air.
U.S. Pat. No. 3,724,534 to Weatherston discloses a multi-zone control system with priority service. A thermostat is provided in each zone and is connected to a controller. The thermostats are polled by a scanner in the controller. Depending on the input the scanner receives from the thermostats, which compare the temperature in the zone with their set points, the controller algebraically adds all of the inputs received from the thermostats and makes a heating or cooling decision based on the thermostat output.
Although these heating and air conditioning systems are designed for zoned structures, they are not best suited for smaller structures such as households where during many times of the day certain areas of the household remain unoccupied for significant periods of time. Rather, these prior art heating and air conditioning systems for the most part, supply conditioned air to each zone where the detected temperature in the zone differs sufficiently from the temperature setting of the thermostat in the zone.
It is therefore an object of the present invention to provide a novel temperature control system and controller therefor.